Computers are known to include a central processing unit, system memory, video graphics circuitry, audio processing circuitry, and peripheral ports. The peripheral ports provide connectivity between the computer and peripheral devices, such as printers, displays, tape drives, and other external memory devices. As is known, displays provide computer users with a visual representation of computer applications (e.g., word processing, drawing, games, TV tuner, etc.) that are being executed by the computer. As the computer executes the computer applications, the central processing unit provides processed data to the video graphics circuitry.
The video graphics circuitry receives the processed data, converts it into display ready data, and provides the display ready data to the display at the appropriate time and rate. For example, if the computer is processing a word processing application and the display is a CRT display having a refresh rate of sixty, the video graphics circuitry converts the processed data into RGB (Red, Green, Blue) pixel data, which may be 8, 16, or 32 bits/pixel, and stores it in a frame buffer, or screen memory. The video graphics circuitry retrieves the stored RGB pixel data from the frame buffer and provides it to the CRT display at the refresh rate.
In the above-described example, the video graphics circuitry is coupled to one display device, which is typical in most computer applications. As such, the video graphics circuitry is dedicated to a single display device. Many computers, however, include an additional monitor port such that two displays may be driven from a single video graphics card. While this allows two displays to be driven from a single video graphics card, both displays will display the same image. In addition, both displays must have the same refresh rate and resolution (e.g., 640 by 480 pixel screen size). If a computer user desires that the two displays display different images, the computer needs to include two video graphics cards
While the two separate video graphics cards allow for two displays to display different images, the video graphics cards are essentially dedicated to their respective displays. In other words, each video graphics card is hard wired to a display port, which couples to one of the two displays. Thus, to change which video graphics card is driving which display, the physical connection or motherboard location of the video graphics card would need to be changed. If the displays are substantially the same, dedicated coupling to one video graphics card or the other does not affect the quality of the images being displayed. If, however, the displays are not the same (e.g., one is an LCD display and the other is a CRT monitor), image quality may vary. Thus, it would be desirable to provide images requiring a higher quality to the display capable of providing the desired quality and to provide images requiring less quality to the display having a lower quality. If the computer user knows which images require higher quality, the user can insure that the images will be processed by the appropriate video graphics card and thus displayed on the desired display. If not, the images may be displayed on the display having the lower quality.
Therefore, a need exists for a method and apparatus that provides for multiple displays to be coupled to a computer without requiring the computer to include a dedicated video graphics card for each display and provides programmable controller.